This application claims the priority of Korean Patent Application No. 2003-88423, filed on Dec. 6, 2003, in the Korean Intellectual Property Office, the disclosure of which is incorporated herein in its entirety by reference.
1. Field of the Disclosure
The present disclosure relates to a method of fabricating poly-Si thin film and a method of fabricating a transistor using the same, and more particularly, to a method of fabricating a poly-Si thin film having high mobility and a method of fabricating a transistor using the same.
2. Description of the Related Art
Poly-crystalline silicon (poly-Si) is applied to a variety of electronic devices such as flat panel displays and solar cells because it has greater mobility than amorphous silicon (a-Si). Generally, poly-Si electronic devices are formed on a substrate of a heat resistant material, such as glass. A method of fabricating a poly-Si electronic device on a plastic substrate has been recently developed. In order to prevent thermal deformations in the electronic device, it is necessary to use a low temperature layer forming process in which a poly-Si electronic device is formed at a low temperature. Such a low temperature process is required in order to prevent thermal shock to a substrate and to suppress process defects that occur at a high temperature in the fabrication process. The use of a plastic substrate for a flat panel display has been developed because the plastic substrate is lightweight, flexible and firm.
A poly-Si thin film transistor (TFT) can be formed on a plastic substrate. However, such a poly-Si TFT must be fabricated at a low temperature because a plastic substrate is heat intolerant.
For example, a method of depositing a material at a temperature of about 400° C. cannot be applied to the plastic substrate, which is thermally deformed at a temperature of 200° C. Methods proposed by Y. J Tung et. al and S. D. Theiss et. al cannot obtain a poly-Si thin film having a large grain size when using a process temperature below 200° C. and a silicon dioxide having a flat-band voltage close to 0 V. (Y. J Tung, X. Meng. T. J. King. P. G. Carey, P. M. Smith, S. D. Theiss, R. Weiss, G. A. Davis V. Aebi, Tech, Digest of SID98, pp. 887-890; D. D. Theiss, P. G. Carey, P. M. Smith, P. Wickboldt, T. W. Sigmon, Y. J. Tung, T. J King, IEDM 98, pp. 257-260)
A conventional poly-Si fabricating method uses chemical vapor deposition (CVD) or plasma enhanced CVD (PECVD). In such a deposition method, a-Si is deposited and then a poly-Si is obtained by annealing the a-Si. Thus, such a conventional method is necessarily accompanied with an annealing process in order to obtain the poly-Si.